1. Field of Invention
The present invention relates to a new and improved process for treating straw and other lignocellulose containing plant material with anhydrous ammonia to improve the nutritional value of the material.
2. Description of the Prior Art
During the years extensive tests have been carried out with the ammoniation of plant material to increase its nutritional value. So far this has not resulted in a satisfactory, economical feasible process which is compatible with the well known Beckmann wet leaching method utilizing caustic alkali (NaOH).
A process for ammoniation of agricultural plant material, such as sugar beet pulp and silage, is described in U.S. Pat. No. 2,293,845, H. C. Millar. The material to be treated is transferred to a heated autoclav and ammoniation with anhydrous gaseous ammonia is carried out under elevated temperature and superatmospheric conditions. The treatment will normally last from 15 minutes to 3 hours. A later patent, Norwegian Pat. No. 97581, Flemming Junker, relates to a somewhat similar process and specifies temperatures of preferably 60.degree.-100.degree. C for the ammoniation treatment under pressure.
Utilizing ammonia under superatmospheric pressures and elevated temperatures, will according to the patent give practically speaking a total dissolution (decomposition) of the lignocellulose in the material.
These prior known methods thus require the use of relatively complicated and expensive pressure apparatus and heating equipment.
The prior art discloses that ammoniation by atmospheric pressure and ambient temperatures has also been investigated. According to British Pat. No. 1,280,922 a number of tests were carried out to determine how the ammonia could be intimately and substantially uniformly distributed into the plant material. A series of preliminary tests were carried out on plant material in the form of whole corn plants cut into smaller chops and having a dry matter content of about 45 percent. The chopped material was introduced into a large plastic bag contained inside an outer drum and ammonia was injected, after the air had been evacuated. The plant material in the drum then was stored for 4 months at room temperature.
It was found that the incorporation of ammonia by such a method was not uniform, and this was particularly noticable at higher nitrogen levels.
Consequently the preferred method of ammoniating at normal pressures and room temperatures was to add ammonia to the plant material in the form of an aqeous solution.
Further Junker, in Norwegian Pat. No. 97581, claims that ammoniation by atmospheric pressure and without a specific heat treatment has serious drawbacks and that the elimination of pressure apparatus will give only 50-60% of the desirable alkali binding and accompanying increase in digestibility.
Accordingly there does not so far exist a practical dry method for the ammoniation of straw and other plant materials containing lignocellulose working at atmospheric pressures and ambient temperatures.